The present invention is directed to photo-active cyclopentadienylplatinum (IV) compounds, and to irradiation-curable silicone compositions containing such compounds as photo-active platinum (IV) catalysts.
Drahnak, U.S. Pat. No. 4,600,484, is directed to a hydrosilylation process involving the addition between silicon-bonded hydrogen compounds and compounds containing aliphatic unsaturation. Drahnak teaches that his process is activated by actinic radiation. Drahnak uses a platinum complex, for example, CpPt(R).sub.3, as a catalyst, where R is a C.sub.1-8 aliphatic organic radical. The Drahnak catalyst has a cyclopentadienyl group, Cp, eta-bonded to a platinum (IV) atom which is substituted with three sigma-bonded aliphatic radicals, and is shown as --Pt(CH.sub.3).sub.3. It is also reported in U.S. Pat. No. 4,600,484, that the cyclopentadienyl group, Cp, in the CpPt(R).sub.3 catalyst can be further modified with organosilyl groups.
In Clark, H. C. and Manzer, L. E., J. Organomet. Chem, 1973, 59, 411, it is reported that (COD)Pt[CH.sub.2 Si(CH.sub.3).sub.3 ].sub.2 can be synthesized using a 1,4-cyclooctadienyl ligand, referred to as COD. However, efforts to eliminate the COD group and substitute it with an alkyl radical to produce a mixed alkyl, organosilicon species, such as a Pt(IV) compound capable of reacting with a Cp(M) compound to form an effective photo-active compound were unsuccessful. More recently, Boardman, L. D. and Newmark, R. A. Mag. Res. Chem. 1992, 30, 481 disclosed that CpPt(IV) complexes having bulky organic groups can be joined to platinum.
It would be desirable therefore to provide additional useful photo-active platinum (IV) compounds to effect the cure of irradiation-curable silicone compositions involving addition between silicon-bonded hydrogen compounds and materials containing aliphatic unsaturation.
Further, it also would be desirable to provide photo-active platinum compounds comprising a cyclopentadienyl group chemically combined to a Pt(IV) group, where the cyclopentadienyl group can be free of organic radicals, or substituted with up to five organic radicals, such as a C.sub.1-22 organic radical, which can include an aromatic radical, such as a phenanthryl radical, or an aliphatic radical, or a mixture thereof; and the Pt(IV) group can have attached to platinum by a carbon-Pt linkage, at least one organosilicon radical, for example, CH.sub.2 Si(CH.sub.3).sub.3, and also include one or more aliphatic or aromatic radicals attached to platinum.